Hi. This is not a question, I had the following problem and I want to share my solution.

-------

I tried to create a new virtual machine with this command:

$ virt-install --connect qemu:///system -n vmTeste -r 512 -f /var/lib/libvirt/images/vmTeste.qcow2 -s 2 -c /media/Data/isos/debian-506-amd64-netinst.iso --vnc --noautoconsole --accelerate --hvm

And I got this error:

ERROR    Unable to deny all devices for vmTeste: No such file or directory
Traceback (most recent call last):
  File "/usr/bin/virt-install", line 1033, in <module>
    main()
  File "/usr/bin/virt-install", line 915, in main
    start_time, guest.start_install)
  File "/usr/bin/virt-install", line 957, in do_install
    dom = install_func(conscb, progresscb, wait=(not wait))
  File "/usr/lib/pymodules/python2.6/virtinst/Guest.py", line 973, in start_install
    return self._do_install(consolecb, meter, removeOld, wait)
  File "/usr/lib/pymodules/python2.6/virtinst/Guest.py", line 1038, in _do_install
    "install")
  File "/usr/lib/pymodules/python2.6/virtinst/Guest.py", line 1009, in _create_guest
    dom = self.conn.createLinux(start_xml, 0)
  File "/usr/lib/python2.6/dist-packages/libvirt.py", line 1277, in createLinux
    if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self)
libvirtError: Unable to deny all devices for vmTeste: No such file or directory

I found the same error looking for in the internet, similar errors including in this list. I tried to solve changing permissions, editing xml and defining the virtual machine, etc.

No long time ago I made some changes to optimize kernel performance for desktop as described here (it's in Portuguese, but can be undertood reading the commands and files) and this changes caused the above errors (in Ubuntu 10.10 and Fedora 14).  I undid the changes and I had no more errors.

Possibly I can be wrong, but it worked for me.
__

Lucas Arbiza

email: lucas.arbiza@gmail.com
celular: +55 (55) 9152 7561

Twitter: http://twitter.com/lucasarbiza
Facebook: http://www.facebook.com/lucas.arbiza
Google Profile: http://www.google.com/profiles/lucas.arbiza
LinkedIn: http://br.linkedin.com/in/lucasarbiza